Bellwork- collision theory

Explain, using collision theory, WHY thefollowing factors increase reaction rate.

a. Increase temperatureb. Increase surface area

c. Increase reactant concentrationsd. Add a catalyst

At chemical equilibrium, no changeoccurs in the amounts of theproducts and reactants.

At equilibrium the system is stable

H2O(s) ⇌ H2O(l) equilibrium at 0°C

Means theprocess is atequilibrium

A reversible reaction is one inwhich the conversion of reactantsto products and the conversion ofproducts to reactants occursimultaneously.

forward 2SO2 + O2 ⇌ 2SO3

reverse 2SO3 ⇌ 2SO2 + O2

As the reaction progresses, reactants formproducts.

The forward reaction rate SLOWS as reactantconcentration decreases.

The reverse reaction rate INCREASES asproduct concentration increases.

2SO2 + O2 ⇌ 2SO3

There are 6 mol SO2 and 3 mol O2 ina closed container

2SO2 + O2 ⇌ 2SO3

2SO2 + O2 ⇌ 2SO3

When the rates of the forward andreverse reactions are equal, thereaction has reached a state ofbalance called chemical equilibrium.

At equilibrium the concentrations of all“species” are constant.

Equilibrium position = the specificconcentrations of all species atequilibrium, which can be calculated forany reaction.

At equilibrium, all three types of molecules are present.

SO2 and O2react to give

SO3

SO3decomposes

to SO2 and O2

If the rate of the shoppersgoing up the escalator

is equal to the rate of theshoppers going down,

then the number ofshoppers on each floorremains constant,

and there is an equilibrium.

In order to reachequilibrium you need

A closed container Stable temperature Low activation energies

Keq = [C]c[D]d

[A]a [B]b

The equilibrium constant (Keq)is a ratio of productconcentrations to reactantconcentrations at equilibrium.

For aA + bB cC + dD

Coefficientsbecomeexponents!

A value of Keq greater than 1 means thatproducts are favored over reactants;

A value of Keq less than 1 means thatreactants are favored over products.

products reactants

= K

18.2 Section Quiz.

1. In a reaction at equilibrium, reactantsand products

a) decrease in concentration.

b) form at equal rates.

c) have equal concentrations.

d) have stopped reacting.